Correctly interpreted, the quasi-periodic oscillations (QPOs) seen in the X-ray spectra of multiple galactic black hole binary systems have the potential to tell us much about both accretion disks and the black holes they surround. In particular, high-frequency (~100 Hz) QPOs feature stationary oscillation frequencies that are comparable to orbital frequencies near the innermost stable circular orbit, suggesting that they can serve as effective probes of the inner disk and, potentially, the black hole itself. Low frequency (~ Hz) QPOs, on the other hand, possess migratory peaks that occupy a frequency range substantially lower than any orbital frequency near the black hole. I will discuss some proposed mechanisms for both types of QPOs, emphasizing the crucial role of magnetohydrodynamic disk simulations in exploring these fascinating phenomena.